from scrapy. exceptions import DropItem
class PriceCheck (object) :
    vat_factor = 1.15
    def process_item(self, item, spider):
        if item ['price']:
            if item ['price_excludes_vat']:
                item['price'] = item['price'] * self.vat_factor
                return item
        else:

            raise DropItem("没有价格 in %s" % item)














